In the fields of glass, metal, ceramic, plastic, semiconductor, etc., maunufacturing, water-repelling, oil-repelling, anti-fogging, anti-contaminating, durability and various other properties are imparted to manufactured substrates by applying a coating film on the substrate surface. By imparting these properties, the value of the manufactured products can be enhanced.
Among well-known methods of providing a coating film on the substrate surface are dipping, spraying, brushing, spin coating, and printing techniques such as the planographic process, relief printing and screen printing. In these techniques, however, the coating solution is merely put physically on the substrate surface, and the adhesion between the substrate surface and coating film is not sufficiently high. Coating film should have a specific thickness. However, it has been difficult using known method to form a coating film having a thickness at the nanometer level which is uniform and free from pin holes.
The inventors have proposed a method for forming an adsorbed film by using a chemical adsorption process. In this method a substrate having hydrophilic groups at the surface is dipped and held in an organic solution containing end functional molecular groups capable of reacting with the hydorphilic groups (hereinafter referred to as a chemical adsorbing material). The adsorbing reaction is brought about at constant temperature in a still or agitated state. Without being bound by the theory, it is believed that the reaction between the hydrophilic groups on the substrate surface and the chemical adsorbing material is brought about very quickly which results in the formation of an adsorbed film.
A previously proposed method of manufacturing a chemically adsorbed film was found to be problematic. That is, where the reactivity between the chemical adsorbing material and the hydrophilic groups on the substrate surface was low, or where highly bulky functional groups or side chains were present in the chemical adsorbing material, the material became space on the substrate due to decreasing reactivity effects or three-dimensional interferences. Thus a long time was required for forming a highly dense chemically adsorbed film. In addition, it decreased the concentration of the chemically adsorbed film, that the saturated adsorption of the chemical adsorbing material to the substrate surface was reduced.
Moreover, even if the reactivity between the chemical adsorbing material and the hydrophilic groups contained in the substrate surface was high, the rate of adsorption was extremely reduced in the last stage of the adsorption. This was due to the seeming reduction of the hydrophilic groups such as hydroxyl groups (commonly termed adsorption sites) on the substrate by the interference between the non-reacted hydrophilic groups and the chemical adsorbing material which behavior and as a barrier formed during the adsorption process.
The present invention, therefore, improves the method of manufacturing the chemically adsorbed film previously proposed by providing a highly concentrated chemically adsorbed film in short period of time.